The present invention relates to the production of a grinding wheel or a rotary abrasive element including an abrasive body made of granular abrasive material, of a binder and preferably of an active and an inactive filler. One of the essential properties required of such a grinding wheel is that it be accurately centered so as to avoid any imbalance during operation.
According to the hitherto known methods for manufacturing grinding wheels the abrasive material, consisting of the actual abrasive, for instance corundum, of a binder and of active and inactive fillers, is put into molds, compressed and burnt in a furnace.
It becomes apparent from the above that the location of the bore which is particularly important for the running of the wheel is determined at a moment when the treatment of the wheel is not yet finished. This is a considerable shortcoming inasmuch as the subsequent treatment of the untreated and sensitive wheel or abrasive body, as well as the burning process thereof, may cause a deformation or warping of the wheel.
According to the present state of the art the hub of wheels, particularly of wheels with large diameters, is formed mechanically after the wheel is finished, i.e. after the cooling of the binder.
However, this operation results in a considerable loss of granular material, since it can only be performed by removing some of the material. Further, this operation takes a long time.
The injection of a synthetic hub has proved impracticable in the case of wheels with large diameters or great volumes, for instance with bores having a diameter of 100 mm or more and depths of more than 50 mm, since the synthetic material employed cools too rapidly during the injection.
High-pressure injection cannot be employed for porous wheels, since such injection causes considerable cracking of the wheel.